The present invention relates to an apparatus for controlling the opening of a control valve in a variable displacement type compressor included in a refrigeration circuit.
A variable displacement type compressor disclosed in Japanese Laid-Open Patent Publication No. 2000-2183, for instance, has a structure in which lubricating oil contained in refrigerant gas flowing in a discharge passage from a compression chamber to an external refrigerant circuit is separated. In other words, the compressor is equipped in the discharge passage with a separation chamber for separating lubricating oil contained in the refrigerant gas. A crank case accommodating a crank mechanism communicates with the separation chamber through an oil return passage.
On the oil return passage, there is provided a control valve which can vary the opening of the oil return passage with a control signal from outside. The refrigerant gas is supplied from the separation chamber to the crank case via the control valve. The control valve regulates the displacement of the compressor.
In the configuration using the control valve, the inlet control valve is closed when the displacement of the compressor is to be maximized. As a consequence, no lubricating oil is supplied from the separation chamber to the crank case through the oil return passage. Especially when the displacement of the compressor is at its maximum, the compressor is at a high temperature, resulting in increasing requirement for lubrication.